The present invention relates to on-chip magnetic devices, and more specifically, to on-chip magnetic structures and methods for relieving stress and minimizing damping losses caused by surface roughness.
On-chip magnetic inductors are important passive elements with applications in fields such as on-chip power converters and radio frequency (RF) integrated circuits. In order to achieve high energy density, magnetic core materials with thickness ranging several 100 nm to a few microns are often implemented. For example, in order to achieve the high energy storage required for power management, on-chip inductors typically require relatively thick magnetic yoke materials (several microns or more), Inductor performance can benefit greatly by adding magnetic film stacks laminated with dielectrics. Two basic configurations are closed yoke and solenoid structure inductors. The closed yoke has copper wire with magnetic stack wrapped around it, and the solenoid inductor has magnetic stack with copper wire wrapped around it. Both inductor types benefit by having very thick magnetic materials.